(CNN) -- Hit-and-run drivers struck two law enforcement officers in separate states within a few hours of each other, killing one of them and seriously injuring another, officials said.

Officer Myron Jarrett, an eight-year veteran of the Detroit police force, was in the midst of a late-night traffic investigation Friday on the city's west side when he was killed by a Dodge truck "traveling at a high rate of speed," Detroit Police Chief James Craig told CNN affiliate WDIV.

Jarrett, 40, was transported to a local hospital, where he was pronounced dead.

"Our prayers and condolences go out to the Jarrett, 12th Precinct, and the entire Detroit Police Department (DPD) family on the tragic loss of one of Detroit's finest, police Officer Myron Jarrett," Craig posted Saturday on Facebook.

A Detroit police spokeswoman said Saturday afternoon that a suspect was in custody, but she declined to name him because he was not yet arraigned.

On the department's Facebook page, however, they posted a picture of the man sought in the hit-and-run -- previously identified by police as Steven Patrick Guzina, 54 -- with the words "in custody" across it. The post did not include Guzina's name.

In Polk County, Florida, south of Orlando, Deputy Sheriff Adam Pennell was injured by a hit-and-run driver as he helped a female driver on the side of a highway. The woman was killed.

Pennell had responded to a call from 33-year-old Jessica Enchautegui-Otero, who had veered off the roadway and hit a tree shortly after midnight, police said.

While waiting for help to arrive, she stood in the grass median on the eastbound side of highway SR 60, near Tiger Lake, police said.

When Pennell spotted Enchautegui-Otero, he pulled his patrol car to the inside lane of the highway, activated his emergency lights and got out of the car to talk to her, the Polk County Sheriff's Office said in a statement.

Moments after Pennell, 25, called EMS, a vehicle heading westbound on SR 60 entered the median and struck them both, police said.

Enchautegui-Otero, of Tampa, was killed and Pennell was seriously injured.

The sheriff's office is offering a $3,000 reward for information leading to the driver's arrest. They say the driver's vehicle will have front-end damage.

If anyone has information about this crash investigation, please call Heartland Crime Stoppers at 1-800-226-TIPS (8477).